I'm trying to Verify that sin(a + b) = sin(a) cos(b) + sin(b) cos(a) with mathematica, but I don't know how to. I've been given a suggestion to use Simplify, but I don't know where/how.

I just started with Mathematica so forgive me if this has a really simple solution. I've searched around but I haven't found anything.


closed as off-topic by AccidentalFourierTransform, Henrik Schumacher, b3m2a1, xzczd, m_goldberg Nov 3 '18 at 17:39

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    $\begingroup$ TrigExpand[Sin[a + b]]. Also FullSimplify[Cos[b] Sin[a] + Cos[a] Sin[b]] $\endgroup$ – Moo Nov 2 '18 at 16:58
  • $\begingroup$ Thank you so much! $\endgroup$ – wznd Nov 2 '18 at 17:59

There's a nifty little function called TrigExpand.

Sin[a + b] // TrigExpand

Cos[b] Sin[a] + Cos[a] Sin[b]


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